A combustion section of a gas turbine generally includes a plurality of combustors that are arranged in an annular array around an outer casing such as a compressor discharge casing. Pressurized air flows from a compressor to the compressor discharge casing and is routed to each combustor. Fuel from a fuel nozzle is mixed with the pressurized air in each combustor to form a combustible mixture within a primary combustion zone of the combustor. The combustible mixture is burned to produce hot combustion gases having a high pressure and high velocity. The combustion gases are routed towards an inlet of a turbine of the gas turbine through a hot gas path that is at least partially defined by an annular combustion liner and an annular transition duct that extends downstream from the combustion liner and terminates at the inlet to the turbine. Thermal and kinetic energy are transferred from the combustion gases to the turbine to cause the turbine to rotate, thereby producing mechanical work. For example, the turbine may be coupled to a shaft that drives a generator to produce electricity.
In particular combustors, a combustion module is utilized to inject a generally lean fuel-air mixture into the hot gas path downstream from the primary combustion zone. The combustion module generally includes an annular fuel distribution manifold and a fuel injection assembly that extends between the fuel distribution manifold and the inlet to the turbine. The fuel injection assembly generally includes an annular combustion liner that defines the hot gas path within the combustor. The fuel injection assembly further includes a plurality of radially extending fuel injectors, also known as late lean fuel injectors that are fluidly coupled to the fuel distribution manifold. The fuel injectors inject the lean fuel-air mixture into the hot gas path downstream from the primary combustion zone. As a result, the combustion gas temperature is increased and the thermodynamic efficiency of the combustor is improved without producing a corresponding increase in the production of undesirable emissions such as oxides of nitrogen (NOx).
The fuel distribution manifold includes an annular flange that extends radially outward and circumferentially around the fuel distribution manifold. The flange includes a plurality of axially extending bolt holes arranged circumferentially around the flange and a fuel plenum that is defined within the flange. The flange is bolted to an outer casing that surrounds the combustor to form a seal therebetween. Fuel is delivered to the fuel plenum through an inlet port that extends outward from the flange.
Current fuel distribution manifold designs use a singular inlet orifice that provides for fluid communication between the inlet port and the fuel plenum. At least one of the bolt holes is skipped in order to provide a sufficient inlet area of the inlet orifice to meet the required fuel flow rate to the fuel plenum during late lean fuel injection operation of the combustor. By skipping the one or more bolt hole(s) an uneven preload between the outer casing and the flange results, thereby potentially resulting in leakage of the compressed working fluid around the flange.
A second issue with having a single inlet orifice is that the flow velocity of the fuel through the inlet orifice is undesirably high. In addition, when cold fuel flows into the inlet port and through the inlet orifice, various thermal issues result at an intersection joint formed between the inlet port and the inlet orifice which may impact the overall durability of the fuel distribution manifold. Therefore, an improved fuel distribution manifold, in particular an improved inlet configuration for routing the fuel into the fuel plenum of the fuel distribution manifold would be useful.